Bug #24727 LOCK_thread_count acquired for too much time

• Submitted: 30 Nov 2006 16:55
• Modified: 30 Nov 2006 19:30
• Reporter: Andrey Hristov
• Status: Not a Bug
• Category: MySQL Server
• Severity: S5 (Performance)
• Version: 4.1, 5.0, 5.1
• OS: Any (All)
• CPU Architecture: Any

[30 Nov 2006 16:55] Andrey Hristov

Description:
Reading sql_parse.cc, dispatch_command(), COM_QUERY:
the mutex LOCK_thread_count is hold for more than usual.
Only
thd->query_id= query_id++;
should be protected by the lock. Even more, it should not be required this code to hold a lock. Better it should be moved to the in 5.0 existing inline function next_query_id(). This function should not use pthread_mutex_lock()/unlock() but
thread_safe_increment() macro.

How to repeat:
sql_parse.cc:

      VOID(pthread_mutex_lock(&LOCK_thread_count));
      thd->query_length= length;
      thd->query= packet;
      thd->query_id= query_id++;
      thd->set_time(); /* Reset the query start time. */
      /* TODO: set thd->lex->sql_command to SQLCOM_END here */
      VOID(pthread_mutex_unlock(&LOCK_thread_count));

[30 Nov 2006 19:30] Andrey Hristov

thd->query assignment should be protected for mysql_list_processes()